<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div {
            width: 200px;
            height: 200px;
            background-color: pink;
        }
    </style>
</head>
<body>
    <div></div>
    <input id="q">
    <script>
        var div = document.querySelector('div');
        // var input = document.querySelector('input');
        // div.innerHTML = "eason";
        // input.value = "eason";
        div.onclick = function () {
            // 行内样式
            div.style.width = '300px';
            // 小驼峰命名
            div.style.backgroundColor = 'red';
        }

</script>
</body>
</html>